1. Field of the Invention
The present invention relates to a spacing member to be attached to a process cartridge, a process cartridge, and an electrophotographic image forming apparatus which process cartridge is capable of being mounted in and demounted from the electrophotographic image forming apparatus.
Here, the electrophotographic image forming apparatus involves an electrophotographic copying machine, an electrophotographic printer (e.g., an LED printer or a laser beam printer), an electrophotographic facsimile apparatus, an electrophotographic word processor and so on.
On the other hand, the process cartridge is constructed by integrating an electrophotographic photosensitive member with at least one process means to act on the electrophotographic photosensitive member into a cartridge so that the cartridge may be mounted in and demounted from the main body of the image forming apparatus.
2. Description of the Related Art
In the electrophotographic image forming apparatus using the electrophotographic image forming process, an image is formed by transferring a developer image formed on a photosensitive drum to the recording medium. In the color image forming apparatus, on the other hand, the developer images of individual colors, as formed sequentially on the photosensitive drum, are transferred in a superposed manner to an intermediate transfer member. And, the color images are transferred altogether to the recording medium. In this case, in order that the portions of the photosensitive drum or the like to be degraded or consumed may be easily handled, there is widely used a process cartridge system, in which those portions are united so that they may be mounted in and demounted from the main body of the image forming apparatus.
One conventional example of the color image forming apparatus using an intermediate transfer member is shown in FIG. 10. In this image forming apparatus (as will be called the “conventional apparatus A”), a photosensitive member unit 350 and an intermediate transfer unit 351 are constructed as independent cartridges. And, a movable side frame 352 is opened by turning it toward the front face of the apparatus. And, the photosensitive member unit 350 and the intermediate transfer unit 351 are individually inserted downward and mounted in the apparatus body.
As another conventional example of the color image forming apparatus using the intermediate transfer member, on the other hand, there is known (in JP-A-11-30944 or JP-A-10-177329) an apparatus (as will be called the “conventional apparatus B”), in which a photosensitive member belt, an intermediate transfer belt and a box for accumulating removed developers are integrally constructed.
In the conventional apparatus B, the photosensitive member belt and the removed developer accumulating box are arranged on the projected lower face of the intermediate transfer belt. As in the conventional apparatus A, moreover, the movable frame is turned and opened toward the front face of the apparatus, and a process cartridge, in which the intermediate transfer member, the photosensitive member and the removed developer accumulating box are integrated, is inserted downward.
As the method for charging the photosensitive drum surface, here is known a contact charge device, in which the charging act is done by bringing a charging roller into contact with the photosensitive drum surface.
The contact charge device has to be disposed in reliable contact with the photosensitive drum surface. For this necessity, the charging roller is pushed to contact with the photosensitive drum by a predetermined pressure.
Therefore, the charging roller is deformed at only one portion if it is stored without any action for a long time. In this case, a deformation may be caused by the creep phenomenon of rubber.
Therefore, the spacer member is sandwiched between the core of the charging roller and the photosensitive drum thereby to space the charging roller from the photosensitive drum. There is known a construction (e.g., JP-A-2-39169), in which the spacing prevents the rubber surface layer of the charging roller from being deformed. Alternatively, there is also known a method (e.g., JP-A-6-316349), in which the pressure and the spacing are caused by using a solenoid.
However, the following problems are accompanied by the prior art thus far described.
With the construction in which the spacer member is sandwiched between the core of the charging roller and the photosensitive drum to space the charging roller from the photosensitive drum, the operator may mount the cartridge in the image forming apparatus without removing the spacer member.
Moreover, the construction for causing the pressure and the spacing by using the solenoid complicates the construction of the image forming apparatus thereby to raise the cost.